Tanning



steed Nov. 25, 1924.

: STATES WILLIAM H. ocxnnsron, or ,1 BOURN, AND THOMAS nunnnnr.cnmvrrcnannl or Y 1 wArEnLoo, NEAR uvnnroon, sperm.

TANNING.

No Drawing.

To all whom it may concern:

Be it known that we, WILLIAM HENRY OCKLESTON and THOMAS BURNEL CAR-MICHAEL, subjects of the King of Great Britain, residing, respectively,in Bourn, in the county of Cambridge, England, and Waterloo, nearLiverpool, in the county of Lancaster, England, have invented certainnew and useful Improvements in Tanning, of which the following is aspecification.

This invention relates to improvements in tanning, and has for itsobject the provision of a process according to which hides and the likemay be tanned by the combined action of a chrome tannage and a vegetabletannage, so that the resultin leather may possess the characteristics ofboth tannings.

In the process of tanning with a chrome tanning agent, it has been usualto bring the said agent to a basic state by the addition of soda ash,and when a combined chrome and vegetable tanning process is employed,using the ordinary chrome salts treated in known manner to render thembasic, the action of the vegetable tanning agent is retarded to such anextent that the hides have to be immersed for a very lon period beforethe vegetable tanning agent has any efi'ect.

We have found by treating the chrome tanning agents according to thepresent invention and using them, and a vegetable tanning agent eithertogether or in succession, that a very rapid and effective tanning isobtained. Further, not only can we employ recognized chrome tanningagents, but we can also employ in this combined tanning process, chromesalts which do not in themselves possess the requisite tanningproperties, such as chromium sulphate, chromium chloride, chromiumnitrate or chromium acetate.

According to one method of carrying out our invention, we immerse thelimed hides in water for several hours, to wash them and extract as muchof the lime as possible before commencing the present process.

We prepare the chrome tanning liquor by adding sutlicient green chromesalts to water to make up a 20 Barkometer liquor; to this we add aceticacid of ordinary commercial strength to give an acidity which, accordingto usual lime water test, is such as requires approximately 20 cubiccentie Application'filed January 21, 1922; 'Seria1No.530,95 6.

meters of saturated lime water to neutralize 10 cubic centimeters of theliquor;

r The vats usually employed .hold 1.250;

gallons and we'find if We addto this quantity of 20 Barkonieten .chromeliquor from 2 to 5 gallons of acetic acid of usual commercial strength,that a suitable liquor is obtained.

The hides are removed from the washing water and suspended in the chromebath so formed, where they remain for, sa 12 hours, by which time theyare comp etely struck-through by the chrome tanning agent.

The hides are then removed and may be horsed-up for a suitable period inorder to drain them.

They are then ready for treatment by the vegetable tannage; thevegetable tanning agent may be any of the usual vegetable tanningliquors of commerce and the treatment may be that usually adopted withsuch liquors for thetreatment of raw pelts. We prefer, however, to startthe vegetable tannage at a Barkometer strength of 80, as this strengthcan be maintained in carrying out the process according to the presentinvention, without any trace of surface hardening of the leather. Thehides are struck-through by the vegetable tannage in about sixdays.

After treatment as above described, the hides are ready for hot pittingin a warm liquor, say from 100 to 150 F., of approximately 150Barkometer strength; they are left in this liquor to fill up.

Alternatively, the hides, after treatment in the acid chrome liquordescribed, above and after washing, may be placed in a floating drumwhich is immersed in a vegetable tanning liquor of from 80 to 90Barkometer strength; the penetration is usually complete in about fourdays, when the hides are ready for hot pitting as before.

We find that the efiect of the vegetable tanning on the hides treatedwith the acid chrome liquor is very rapid and penetrating so that thetime taken in theordinary tanning process is very considerably curtailedby the employment of our process.

In some cases. we may combine the acid chrome and the vegetable tanningsolutions in equal proportions to form the one liquor,

in which case the vegetable tanning solution would be of weakerstrength, say 30 to40 Barkometer; the hides may, after treatment in thiscombined liquor, be subjected to treatment in a vegetable tanning liquoroi suitable strength, or may be treated in a succession of vegetabletanning liquors of increasing-strengths. a

The leather product ofhour process has a high percentage increase ofweight on the limed pelt weight, possesses a high tensile strength andhard wearing qualities, and is specially)e suitable for.- sole leather;and leather ltin'g; i

Having now full described our invention, we declare that w at we claimand desire to secure by Letters Patent, is

1. The process of tanning, which consists in treating de-limed hideswith an acidified fireen chrome liquor of substantially 20 arkometer,and with vegetable tanning so liquor. I 2. A process for tanning, whichconsists in' treatmg de-limed hides m a mixture of equal parts of chromeliquor of substantially 20 Barkometer, 'and a ve%table tanning liquor offrom 30 to 40 arkometer.

In testimony whereof we aflix our signatures in presence of twowitnesses.

y W. H. OOKLESTON.

THOMAS BURNELL CARMICHAEL. -Witnesses J osnrn E. Hms'r,

, Maneunma J om

